docs: def get_dual_rmetric( self, invert_h = False, mode_inv = 'svd' ):
          """
          Compute the dual Riemannian Metric
          This is not satisfactory, because if mdimG<mdimY the shape of H
          will not be the same as the shape of G. TODO(maybe): return a (copied)
          smaller H with only the rows and columns in G.
          """
          if self.H is None:
              self.H, self.G, self.Hvv, self.Hsvals, self.Gsvals = riemann_metric(self.Y, self.L, self.mdimG, invert_h = invert_h, mode_inv = mode_inv)
          if invert_h:
              return self.H, self.G
          else:
              return self.H